1. Field of the Invention
This application relates to an adapter for transferring dry chemicals to and from a storage container, such as a railroad car, truck, ship or storage tank and related system and method. The invention is particularly suitable for use with particulate chemicals which form hydrates which can contain difficult to handle particles or which include particles which tend to agglomerate, such as soda ash.
2. Description of Related Art
Various means have been described for transferring dry materials out of containers. For example, U.S. Pat. No. 3,512,842 describes a method for unloading railcars in which a slurry is formed inside the railcar and then is pumped out. Such a process has numerous drawbacks, however, including the risk of overflowing or foaming within the car; the need for specialized railcars adapted for use in the slurrying process; the possibility of corrosive solutions being formed and damaging the railcar; problems with residual moisture causing caking in subsequent shipments; and the formation of hard, slowly dissolving lumps when liquid is added to a large quantity of solid. A similar approach is described in U.S. Pat. No. 4,189,262.
Eductors have been used and are still used to transfer dry chemicals as a slurry, solution or solid. For example, liquid driven eductors have been used to slurry dry polymers and activated carbon in the water treatment industry and to transfer fly ash in the electric power industry. Also air, steam, and liquid driven eductors have been used for transfer of solids. However, problems are known to exist with eductor-based handling systems.
For example, air driven eductors require a high power input and air flow per unit mass of solid conveyed resulting in high energy costs and higher capital cost for dust collection equipment. Steam driven eductors are used to create a vacuum for pneumatic conveying of dry solids to a solid-liquid mixing apparatus. The systems using steam driven eductors which are known to the inventors require a large amount of support equipment including a barometric leg for condensing the steam with modifications for solid-liquid mixing, and a large steam supply. Since the solid is conveyed by vacuum, the steam driven eductor system is limited by economics to installations where it can be located near, e.g. within a few hundred feet of, the container of dry chemical.
Liquid driven eductors do not require large volumes of air or steam and can be used to transfer dry chemicals from a container, such as a railcar, forming a solution or slurry of the chemical in the liquid carrier medium. Liquid driven eductors are known to be successfully used to prepare dilute solutions of polymer in water as well as to transfer insoluble materials, e.g. activated carbon, to storage as a slurry.
Commonly assigned U.S. Pat. No. 4,884,925, discloses an apparatus and method for transfer and slurrying or dissolving hydratable dry bulk chemicals hereby incorporated by reference. Briefly, this patent discloses an apparatus for the transfer of dry chemicals. The disclosed apparatus has a sealed solvation hopper positioned between a liquid driven eductor and a fitting for connection to a storage container such as a railroad car. At the inlet end of the solvation hopper is a chemical inlet pipe which connects the interior to the exterior of the hopper. Surrounding the chemical inlet pipe are a plurality of nozzles for introduction of solvation liquid into the hopper. The nozzles are disposed such that the solvation liquid washes the interior surface of the hopper to prevent plugging by hydrates (solvates) which may be formed. At the outlet end of the hopper is connected to a suction opening of the liquid driven eductor.
In operation, liquid flowing through the eductor creates a suction and draws dry chemical out of the storage container and into the hopper. In the hopper, solvation liquid is supplied through the nozzles to wet the dry chemicals and to wash the surfaces of the hopper, pushing the wetted material toward the outlet end of the hopper. At the outlet end of the hopper, the wetted material is sucked out of the eductor where it is combined with the flow of eductor liquid. The material leaving the eductor is recovered and sent to storage or directly for processing. The process and apparatus are particularly useful for handling soda ash.
Dry bulk solids, particularly soda ash, shipped in a particulate state are removed from the shipping containers as recited above and converted directly into a hydrate. By hydrated it is meant that the dry chemical is combined with water to form a mixture of water and particulate matter. The mixture can include a slurry and/or solution. Because such large quantities of dry particulate matter are handled there is a continuing problem of dealing with large particular impurities, insolubles, and soda ash which is lumped together by exposure to moisture. In particular, lumps of soda ash which form, are in the form of sodium carbonate decahydrate and are difficult to dissolve causing plugging in the hydrator, particularly in the mixing cone of the hydrator of the type disclosed in U.S. Pat. No. 4,884,925.